The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device in which solder dams can be formed with exceptional ease. Solder dams are required to be formed when mounting an electronic part such as an LSI chip for driving a liquid crystal display device on one of the two glass substrates of a liquid crystal cell, to prevent molten solder for connecting the electronic part to the circuit wiring from flowing beyond a desired area along the wiring sections.
A liquid crystal display device in which an electronic part such as an LSI chip for driving electrodes is mounted on one of the two glass substrates of the liquid crystal cell thereof has recently come to be used widely.
In recent years, "Chip-on-Glass" technology has been studied in order to reduce the size of display devices, to increase display content, and to improve reliability as described in "Chip-on-Glass Technology for Large Scale Automotive Displays", Electronic Displays and Information Systems, SP-565, International Congress & Exposition, Detroit, Michigan, Feb. 27-Mar. 2, '84. Through chip-on-glass technology, integrated circuits are bonded in chip form directly onto a glass substrate of liquid crystal display device, for example, as described in U.S. Pat. Nos. 4,145,120 and 4,283,118.
In the case of such liquid crystal devices, it is normal practice to form solder bumps of a certain amount of solder on the connecting terminals (bonding pads) of electronic parts. Solder-receiving sections are provided beforehand on the wiring side of the glass substrate, at positions corresponding to those of the above bumps, i.e., the terminals on the electronic part. When performing the mounting operation, the solder bumps on the bonding pads of the electronic part are registered with the corresponding solder-receiving sections on the substrate. The solder is then melted by heating it by the reflow method or a similar method, and is allowed to harden, thus providing electrical connection and mechanical bonding and support.
In the above mounting operation through soldering, it is necessary that the solder of the bumps hardens after it has been sufficiently wetted and stuck to the the metal surface of
the solder-receiving sections. If molten solder of bumps is allowed to flow freely over the clean wiring surface of the substate (while the wiring of liquid crystal display devices may be made of either transparent conductive films or metal films, in practice the latter is almost always adopted for those on which electronic parts are to be mounted), the height of the solder bumps is decreased. In such cases, the way the solder flows is different in different parts (depending on the width of the metal film wiring or on whether the solder-receiving section is almost directly connected to a transparent conductive film wiring, etc. As a result, the shape and height of the solder bumps, which were the same everywhere at first, become different in different parts, resulting in an uneven condition of the soldering between the electronic part and the wiring on the substrate. Electrical connection or mechanical support to be obtained through soldering can consequently become inadequate at some soldering positions.
In this context, Japanese Patent Laid-Open No. 252534/1986 (Japanese Patent Application No. 93670/1985), conceived by one of the inventors of the present invention, et al., proposes the formation of solder flow stoppers (solder dams) which consist of photosensitive polyimide resin films formed through photolithography, over the wiring surface. It is true that this prevents the solder from freely flowing along the wiring when performing soldering, allowing the soldering to be effected reliably at a plurality of positions. However, it involves an increase in the number of production processes as well as higher cost.